RedfishPkg: Change OPTIONAL keyword usage style

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3760

Update all use of ', OPTIONAL' to ' OPTIONAL,' for function params.

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Abner Chang <abner.chang@hpe.com>

RedfishPkg/PrivateLibrary/RedfishLib/edk2libredfish/src/service.c

@@ -227,7 +227,7 @@ DecodeResponseContent (
 EFI_STATUS
 RedfishBuildUrl (
   IN  REDFISH_CONFIG_SERVICE_INFORMATION *RedfishConfigServiceInfo,
-  IN  CHAR16                        *RelativePath,   OPTIONAL
+  IN  CHAR16                        *RelativePath    OPTIONAL,
   OUT CHAR16                        **HttpUrl
   )
 {